A few authors who might not have had long glorious careers but did some fabulous work and I don't see them mentioned often: Eando Binder "Adam Link, Robot", Lester Del Rey "Nerves", Poul Anderson "High Crusade" & "Tau Zero", and even A.E. Van Vogt (who revisits the same themes too much for my taste), has some I like, like "Black Destroyer", "Weapon Shops of Isher", and "Empire of the Atom"